1. Field of the Invention
The present invention relates to an apparatus and a method of information processing, a program, and a recording medium, and particularly to an apparatus and a method of processing information, a program, and a recording medium which can suppress image quality degradation as small as possible and can process information efficiently with a small delay.
2. Description of the Related Art
Heretofore, for communication paths, there are cable communication using cables, and radio communications using radio. Radio communication paths such as WLAN (Wireless Local Area Network), Bluetooth, UWB (Ultra Wide Band), and WiMax (Workwide Interoperability for Microwave Access) have more limited bandwidth than those of cable communications paths. On this account, in order to transmit moving images through radio communication paths, it is necessary that the moving images for a transmission target are encoded and compressed to reduce a data volume.
For this type of codec for the moving image that is well known before, for example, MPEG (Moving Picture Experts Group) -2, MPEG-4, and AVC (Advanced Video Coding) are named. In these codecs, since processes for taking the correlation between pictures and processes for motion compensation are performed, a codec delay in association with signal processing occurs for about 0.1 seconds to 0.5 seconds. In addition, in these codecs, since compressed bit streams have the correlation between pictures, when a loss occurs in a certain picture, the loss is propagated to the subsequent picture, and the influence of the loss becomes great on image quality deterioration.
On the other hand, since compression is performed in pictures in DV (Digital Video), JPEG (Joint Photographic Experts Group), JPEG2000, the codec delay is suppressed in a single picture, and the influence due to the loss is closed within the picture. Consequently, these codecs are suited for implementing transmission with a small delay in radio communication paths and for improving error tolerance in communication paths.
For example, in JPEG2000, discrete wavelet transformation (hereinafter, simply referred to as “wavelet transformation”) is used. In discrete wavelet transformation, for a base band signal that is an original image, one-dimensional wavelet convolution is applied to individual horizontal pixel rows, and the image is divided into two sub-images, a sub-image including low frequency information and a sub-image including high frequency information. Moreover, for each of the sub-images, the similar convolution is applied to individual vertical pixel columns, and the images are divided into two sub-images, sub-images with low frequency information and high frequency information.
Consequently, as shown in FIG. 1, a base band signal 1 that is an original image are decomposed into four subbands, that is, four sub-images (HH, HL, LH and LL). In addition, each of the sub-images has one-fourth of the size of the original image, and includes the number of data points that is one-fourth of the original image. Moreover, subscripts corresponding to the sub-images each indicate signal frequency components corresponding to the vertical and horizontal pixels. For example, (1) a sub-image HL includes high frequency image information from horizontal wavelet convolution and low frequency image information from vertical wavelet convolution, and (2) a sub-image LH includes low frequency image information from horizontal wavelet convolution and high frequency image information from vertical wavelet convolution.
Such wavelet transformation is repeatedly applied to an obtained sub-image LL. In other words, as shown in FIG. 1, suppose an original image is subjected to wavelet transformation to obtain sub-images 1HH, 1HL, 1LH, and 1LL (not shown) at the first decomposition level. The sub-image 1LL is further subjected to wavelet transformation, and divided into sub-images 2HH, 2HL, 2LH, and 2LL (not shown) at the second decomposition level. The sub-image 2LL is further subjected to wavelet transformation, and divided into sub-images 3HH, 3HL, 3LH, and 3LL at the third level. As described above, wavelet transformation is repeatedly performed, and in a transformed signal 2, the sub-images have a hierarchical structure.
As described above, in sending image data compressed by using wavelet transformation, there is a method in which all data in a single row at a single decomposition level (as the same row of the subband (for example, 3HL, 3LH, and 3HH) is formed into a block of the adjacent row) is together transmitted, whereby an image is made visible in advance during transmission as well as the transmission is allowed to finish at earlier time when the image is not a desired one (for example, see Patent Reference 1 (JP-A-8-242379)).
In the case of this method, for example, in the transformed signal 2 subjected to wavelet transformation and having the hierarchical structure as shown in FIG. 2, the individual rows of a sub-image 2LL are transmitted from above in order of 2LL-1, 2LL-2 and so on. Subsequently, the individual rows of a sub-image 2HL, a sub-image 2LH, and a sub-image 2HH are in turn transmitted (for example, in order of 2HL-1, 2LH-1, 2HH-1, 2HL-2, 2LH-2, 2HH-2 and so on). Then, the individual rows of a sub-image 1HL, a sub-image 1LH, and a sub-image 1HH are in turn transmitted from above.
In addition, a coding system with a small delay is proposed as a codec to implement a small delay in which JPEG2000 is split into tiles for coding (for example, see Non-Patent Reference 1 (KDDI R & D Laboratories, “JH-3000N”, Product Catalog, April, 2006)). This is a method in which a single screen is split into a plurality of tiles and each row is encoded in parallel. A single tile is compressed as similar to a single JPEG2000 image. Therefore, it can perform processing in the particle size finer than that of a picture, and the codec delay can be suppressed to a single picture or below.
Moreover, there is a codec technique using line based wavelet transformation. This technique is that horizontal wavelet transformation is performed every time when a single line of the base band signal of the original image is scanned, and vertical wavelet transformation is performed every time when a certain line is read. For example, suppose vertical wavelet transformation is performed for every eight lines of the base band, in the case of three wavelet decomposition levels, with respect to these eight lines, a single line of a lowest sub-image 3LL, a single line of each of subbands 3H (3HL, 3LH and 3HH) at the next lowest level, two lines each of the subbands 2H (2HL, 2LH and 2HH) at the subsequent level, and four lines of a highest level 1H (for each of 1HL, 1LH and 1HH).
In addition, a set of lines of the subband is referred to as a precinct. In other words, a single precinct includes the plurality of lines that is a processing unit of line based wavelet transformation. Moreover, a set of lines of the subband at each level in the precinct (except 3LL, it is formed of three subbands) is referred to as an align unit. In other words, a single precinct of the subband is configured of four align units (3LL, 3H, 2H and 1H).
For example, a precinct (a shaded area in the drawing) having eight lines in the base band signal 1 on the left side in FIG. 3 is configured as shown on the right side in FIG. 3 as four lines for each of 1HL, 1LH, and 1HH in 1H in the transformed signal 2 after line based wavelet transformation (a shaded area in the drawing), two lines for each of 2HL, 2LH, and 2HH in 2H (a shaded area in the drawing), and a single line for each of 3LL, 3HL, 3LH and 3HH (a shaded area in the drawing).
As similar to the tile splitting of JPEG2000, the process of line based wavelet transformation can be performed by decomposing a single picture in finer particle size, and this transformation is used to intend to make delay small. However, in the case of line based wavelet transformation, since it is the split by a wavelet coefficient, not the split in accordance with the base band signal 1, different from the tile splitting of JPEG2000, the transformation also has the characteristic that degraded image quality like block noise will not occur on the border between tiles.
In the case in which data compressed by using the line based wavelet transformation like this is sent through radio communication paths, as a method of increasing the resistance against losses, data in lower frequency bands can be in turn sent as similar to the existing transmission of progressive coded data (JPEG2000 code streams).